Copper base alloys



3,017,268 CPPER BASE ALLOYS Matti J. Saarivrta, Piaiuield, NJ., assigner to American Metal Climax, line., New York, NSY., a corporation of New York File-tl May 9, 1960, Ser. No. 27,680 8 Claims. (Cl. 7S-154) This invention vrelates to copper base alloys essentially containing titanium, tin and chromium. The alloys of this invention have a minimum copper content of 90% and are age hardenable. They possess highly desirable properties attained preferably by working and heat treatment which properties make the material particularly suitable for various electrical and yelectronic applications including the making of electrodes and their holders for resistance welding machines, electrical contacts, springs and numerous other items requiring reasonably good strength, conductivity, ductility, resistance kto corrosion and stability to the extent that the desirable properties aud characteristics of the alloy are retained at elevated temperatures. Y

For the making of springs, contactors and the like, age hardenable copper base alloys containing beryllium are used quite extensively. Commercie-illy available beryllium alloys containing, for example, 0.4 to 0.7% beryllium, 2.3 to 2.7% cobalt, balance copper possess attractive mechanical properties in several respects including a tensile strength of as much as 100,000 p.s.i lcombined with electrical conductivity of about 48% that of pure copper. Such a combination of properties are exceedingly diicult to obtain since in the case of most copper alloys having a tensile strength of about 90,000 to 100,000 p.s.i. or higher, the electrical conductivity is rarely above 30% that of pure copper. K

Although the aforesaid beryllium-copper alloys are satisfactory for various electrical and electronic applications with respect to meeting mechanical and physical property requirements no-t met by most other copper base alloys, such alloys have the drawback that they are rather difficult and costly to make. Furthermore, these alloys require the use of beryllium which in addition to being expensive is also an 'extremely toxic substance necessitating special precautions in the making and subsequent processing of such alloys. Then too, whereas such beryllium copper alloys are suitable for rather limited high temperature applications, extreme brittleness is encountered at temperatures in excess of about 22S-250 C. leading to failure of the alloy. Accordingly, there is an urgent need for materials which not only possess satisfactory properties at ordinary temperatures of operation but which also are capable of withstanding higher temperatures over prolonged periods of operation without excessive deterioration of the alloy by embrittlement or otherwise.

it has now been discovered that quaternary alloys of copper containing titanium, tinfand chromiurnwhich al-v loying ingredients are present in relatively small amounts not exceeding 10% in the aggregate provide age hardenable copper base alloys that can be readily processed'by appropriate treatment to provide physical andmeehanical properties that compa-re favorably by comparison with the aforesaid beryllium-containing copper base alloys. The new and novel alloys of this invention not only possess satisfactory propertiesV and characteristics at ordinary tet temperatures of operation but are also markedly superior with respect to their ability to withstand significantly higher temperatures without failure. The alloys of the presentginvention have the further important advantage of being much more economical to produce than therpreviously mentioned copper-beryllium-cobalt alloys. At the same time, the serious toxicity problems associated with the use of beryllium are completely eliminated.

It is therefore, an object of this invention to provide copper-titanium-tin-chromium alloys possessing excellent mechanical properties and characteristics for applications and uses requiring a copper base alloy of medium strength and reasonably good electrical conductivity. Y

lt is another object of this invention to provide age hardenable copper-titanium-tin-chromium alloys that possess improved properties compared with beryllium-copper alloys especially with respect to retention of said properties under service conditions involving lelevated temperatures appreciably higher than 250 C.

Another object of this invention is to provide new and novel alloys that substantially meet the requirements with respect to tensile strength, electrical conductivity and other properties satisfied by heryllium-coppers without incurring the high cost Vof* production and toxicity problems associated with such beryllium-containing alloys.

Other objects and advantages Will become readily apparent as this specification proceeds.

The copper base quaternary alloys of this invention generally contain from 0.3 to 4% titanium, 0.5 to 5% tin, 0.05 to 2% chromium, the balance being copper which is present in all instances in the amount of at least with respect to the overall alloy composition. Phosphorus and/or silver may be optionally included in amounts not exceeding 0.05 and 1% respectively without significantly altering the properties of the resulting alloys although the presence ofphosphorus in amounts appreciably above 0.02% does effect some reduction in the electrical conductivity of the material. The preferred composition of the quaternary alloy consists of from 1 to 3% titanium, 2 to 4% tin and 0.2 to 0.8% chromium, balance copper, with the proportion of titanium to tin being in the ratio of approximately 1:1.7 respectively. Optimum properties of the alloy are obtained with the use of from 1.3 to 1.7% titanium, 2.2 to 2.9% tin and 0.3 to 0.6% chromium. All of the foregoing percentages refer to the actual content of the various alloying elements in the resulting alloy product.

Although tough pitch copper may be used in makingl the alloys of the present invention, it is definitely preferred to make said alloys with initially oxygen-free copper. Such coppers include electrolytic cathode copper, copper made in a reducing atmosphere such as OFHC brand copper, or copper made using an inert atmosphere, a vacuum or under a charcoal cover, Chemically deoxidized copper obtained by the treatment of oxygencontaining copper with phosphorus, lithium or other deoxidiz'ers may also be used in making said alloys.

The alloys can be made according to standard alloying methods such as melting the Copper in an induction furnace and adding the desired amounts of titanium, tin and chromium and possibly other ingredients such as silver and phosphorus when the melt is at a temperature of about 1300 C. The alloying ingredients may be in any form suitable for a-lloying purposes such as metal sponge, master alloys, etc. If desired, the chromium may be included Patented Jan. f6, 1962' in appropriate amount in the form of a copper master alloy (5% Cr) along with the copper at the time of preparing the copper melt in which event only the titanium and tin need be subsequently added. If desired, phosphorusdeoxidized or phosphorized copper may be used in preparing the initial melt whereby the separate addition of phosphorus at a later time need not be made if phosphorus is to be included in the alloy. After alloying, the ternperature of the melt is lowered and held at about 1200" C. with the alloy being stirred and allowed to settle for about 5-10 minutes after which it is cast in accordance with conventional practices.

In making the alloy, it is impor-tant that an inert protective atmophere consisting of argon, helium or other inert gas be used throughout the entire operation including the casting step. The use of non-oxidizing gases such as carbon monoxide, nitrogen or hydrogen should be avoided since such gases react in varying degrees with one or more of the alloying ingredients and especially with tit"- nium. If carried out correctly, the melting, alloying and casting procedure presents no diiculties and sound castings are readily produced using copper or any other suitable molds in casting the alloy.

Microscopic study of the cast structure of representative quaternary alloys containing, for example, 1.5% titanium. 2.5% tin and varying amounts of chromium ranging from 0.06 to 1.6% revealed the presence of three phases consisting of the alpha phase, a second phase consisting of Ti-Sn rich compound and a third phase which closely resembles in color and appearance the chromium-rich phase found in the copper-chromium binary alloys. It was observed that the amount of the third phase was increased upon increasing the chromium content of the quaternary alloy. These observations indicated that chromium does not combine with titanium and tin present in the system but forms a compound with copper and, for best results, the chromium content of the alloy should be a minimum of 0.3%. It was also ascertained that this third phase becomes substantially completely dissolved by solution annealing the alloy at about 875 C.

The alloys of the present invention possess excellent hot workability upon being preheated a-t about 800 to 850 C. said hot working being effected either by hot rolling or forging as may be desired. By way of illustration, a 300 pound casting in the form of an 8 inch diameter billet was readily hot forged after preheating for one hour into square rod material of 2.5 and 1.5 inch sizes respectively with no diiii'cult'y. The alloys may also be readily cold worked' to reductions un to 90% and even higher by rolling or Wire drawing without difficulty.

The' conventional heat treatments used to obtain age hardening in copper alloys may be satisfactorily used to harden the alloys of the present invention. Solution annealing is effected by heating the alloy to temperatures gen` erally ranging from about 825 to 890 C. for from a few minutes to about an hour or so depending on the solution annealing temperature used, it being preferred, however, to utilize a temeprature between 850 and 885 C. and optimally about 875 C. for about 30 minutes after Which the alloy is quenched. Age hardening for from 2 to 4 hours at temperatures generally between 400 and 475 C. and preferably at about 450 C. is conducive to development of maximum strength. If electrical conductivity of about 40 to 50% I.A.C.S. is required as an essen-tial property of the alloy, the optimum combination of properties with respect to strength and conductivity are produced by extending the heat treatment period to generally Vfrom 6 to 8 hours utilizing the preferred age hardening temperature of about 450 C. Cold working by wire drawing prioi to precipitation hardening of the alloy appreciably reduces the aging time required for development of optimum properties including electrical conductivities between 40 and 5 0%.

The cast alloy processed, for example, by solution annealing at 875 C. for from 15 to 30 minutes, quenched in Water and age hardened for from 6 to 14 hours at 450 C. possesses a tensile strength ranging from 60,000 to 80,000 p.s.i., electrical conductivity of from 35 to 50% I.A.C.S. and elongation values (percent in 2 inches) up to 10%. Prior to age hardening, the tensile strength of the solution annealed material generally ranges from 45,000 to 55,000 p.s.i., the electrical conductivity is only about 7% I.A.C.S. and elongation is about 40% with reference to a representative alloy of the same composition containing 1.5% titanium, 2.5% tin, 0.5% chromium, balance copper.

The alloys of the present invention are readily processed from cast material into Wrought products such as bar stock, wire, sheet material, etc. utilizing typical processing steps consisting of (a) preheating the cast alloy at 800 to 850 C., (b) hot working as by rolling or forging, (c) solution annealing at about 875 C. for about 30 minutes, (d) quenching, and (e) age hardening at about 450 C. for about 6 to 8 hours. Cold working with intermediate annealing may be additionally included in the processing steps with the alloy being subjected to precipitation hardening either in the cold Worked state or in the solution annealed condition following quenching.

In the accompanying drawing, the effect of age hardening solution annealed wire of nominal composition (1.5% Ti, 2.75% Sn, 0.6% Cr, balance Cu) for varying periods of time at 450 C. is graphically shown with reference to Various properties of the alloy. In these tests a 1 inch diameter casting was preheated at 850 C., hot rolled to 0.25 inch diameter rod, annealed at 875 C. for 30 minutes, quenched, cold drawn to 0.132 inch diameter wire and solution annealed at 875 C. for 30 minutes. Specimens of the solution annealed material were then subjected to aging at 450 C. for varying periods of time up to a maximum of 14 hours as indicated in the drawing. The FIGURE shows that maximum precipitation hardening of the alloy occurs during the second through fourth hours of heat treatment but the electrical conductivity is only 20 to 25% I.A.C.S. with such heat treatment. Overaging occurs after 4 hours with some loss of tensile strength but with an increase in elongation and conductivity values with the optimum combination of properties being obtained after aging for 6 to 8 hours. In this condition tensile and yield strengths of about 95,000 and 70,000 p.s.i. respectively, elongation of from 13 to 16% and electrical conductivity values of from 40 to 46% I.A.C.S. are characteristic properties of the alloy. Hardness values of this representative alloy range from 75 VPN in the solution annealed condition to about 200 VPN after aging for 8 hours.

Tensile strengths appreciably abo"e 100,000 p.s.i. with electrical conductivity better than 40% are readily obtained by aging the alloy after cold working-by wire drawing. The properties obtained with specimens of 0.081 inch diameter wire of typical alloy compositions consisting of 1.5% Ti, 2.5% Sn, 0.7% Cr, balance copper (Alloy A) and 1.5% Ti, 2.75% Sn, 0.7% Cr, balance copper (Alloy B) that were cold worked 64% and aged for Varying periods up to 5 hours at 425 C. are summarlzed 1n Table I.

Table I Aging Yield Elonga- Electritlme at Tensile strength tion (percal con- Alloy 425 C. strength .1 o centin ductivity (hrs.) (ps1.) odset, p.s.i.) 2 inches) (percent I.A.C S.)

.From 'the foregoing, it becomes apparent that-inthe case Table 111 PI Cold drfawnwm subie-ded to apprec1ab1e-c01d-work [Alloy Composition-1.5%.Ti,2.5% sn,o.5% or, balance oui ing, the aging time for the development of optimum properties is actually between 2 to 3 hours at 425 C. `Specimens cold drawn to reductions below about 40% were 5 S01- 2111- s011111- f i Y Sol. aunealed and nealedeold generally found to require close to 3 hours for obtaining and at heatmated Worked electrical conductivities` of at leastY 40% whereas those Property 875 C- 01450" C- and heat quenched for 6-8 treatedaty specimens that were cold drawn 53% or more attained hours 450 Ufer over 40% I.A.C.S. electrical conductvity after aging for 011011IS1 only approximately 2 hours. 10

Properties of 0.05 inch thicksheetivvere determined Ult-Otg/Slffength -S-1- 50'551000 90120883 98-1151000 on a representative alloy containing 1.5% Ti, 2.5% Sn, P 0172005501:" 70-75100 "551135500 i ropoltionallimlg (ps 415-60000 75,000 05% Cr, balance C11, the 111211611211 111, 1111811102111@ 196mg Modulusomastmtyms, 1mm, 000 processed by hot rolling, solution annealing and cold yroll- Elongaiion (percent in 2 inglesi.. 3540 13-17 il ing to varying reductionsfrom 16 to-80%` after which 15 Drcglty (09mm 1000000 l 37 the specimens were aged' fromi2'to hours'at 425 and vielrers hardness vijl\f)'. "00' 20o-210 "m2013550 450 C. respectively. With cold rolling to reductions Ell'afductmty (Percent 7 M -48 4o 415 of 16.6, 28.6 and 37.5 subseguent aging ateither 425 Specific gravity g./cm.1) 8.8 or 450 C. generally resulted in electrical conductivities pf at least 40% I.A.C.S. only after aheat treating time 20 1005111511 thickness sheet material. of 6 hours. With reductions of 50% orhighe'r, hovvi A ai e ever, conductivities of at least 40% I.A.C.S. were ob- Hoy Composition- 0 4% B26% Cokalmc Cu] tained after h eat treating the cold rolled sheet material Sm en at 425 C' for genefauy from 4` t0 6 OUIS heat Solan- SoLanncalr-d neale'dcnld treatina time required at 450 C. is' appreciably less as 25 Property3 nealed and heat Worked c treated hard and will be evident from lthe data` submitted in Table II heattreated wherein other property values of the sheet material are listed. ultotrr/isiie siit'engtli (p.s.i.) 34-50, 000 8800s, 000 98-116, 000 O Se 0.1'7Zo1iset lis-28,000 70-90000 944-108.000 Proportioniillimit 8-18, 000 Lits-08,000 (s0-50,000 Table II Moduius olelasiicity (p. iii-i7, 000, 000 Y Elongation(pereentin2inch 20-35 8-15 5-12 A. ALLOY GOLD WoRirED 50% (ROLLED) Dcetllty (percent reduction in 32 I Eckters h ardnes (7 P lT). 65-85 190-230 210-240 Heat Yield 'Elonga- Electrical e0 rica con ne ivi y per. Aging treat- Tensile, strength tion (per- Hald- 0011-0110- @mit IA-C;S) 2025 453-52 45-48 temp, ing stl-@mth (0,1% Orr. Cantin npss tivity Svelc grvltv (alem) 8.8 C.) time (psi.) s0t,p.s.i.) Zinches) Y(VPN) Ityreit (hrs') I m' 2Valiiesfrom C.D.A.Publieation No.54ei1titledBeryllium Copper issued in 1958 by the Copper Development Association.

` a. v 55 g lggg lgggg g 28,8 The alloys of the present invention exhibit good ducg' ggg 1275, ggg gg 38 40 tility and strength at elevated temperatures asv will be 42g 5 1171000 1001000 `90 4020 apparent from; the properties listed in Table IV. The 425 6 115,000 95,000 8-0 40-0 short time Ktensile properties of the 15% Ti 25% Sn 92, 00 9.0 250 40.0 45g 58,000 10.0 23e 43.0 0.5% Cr, balance Cu, alloy in the form of 0.25 inch diameter rods were determined at 300 and 425 C. after B. ALLOY COLD WORKED 66. 5% 45 solution annealing at 875 C., quenching and heat treating at 450 C. for 6 hours.

. o 98,000 s0, 000 3.0 5. 0 425 2 12s, 000 111,000 8.0 32.0 Table IV 425 3 127, 000 110,000 8.0 35.0 425 4 esta .it ils 425 5 11,000 T t' t -t 425 0 117,000 98,000 10.0 43.0 50 Property es 111g empale ure 450 3 114, 000 93, 000 11.0 42. 0 450 e 113,000 92,000 11.0 44.0 300 C. 425 C.

C. ALLOY COLD WORKD 80% Ultimate tensile strength (psi) 75, 000 50, 000

5 55113450454 a tra it le siteng o se p 0,0 ,000 o 107, 000 90. 000 B 0 235 810 Proportional limit iopsi 32, 000 425 2 127,000 109,000 8-0 37-0 Modulusofelastieity (p. 20,500,000 21,000, 000 g 287 llcnglaion (percentii2i-nehes) 11.0 42g 5 1193000 98h00 11:0 :I: 43: 0 ucti i y (percent re uetion in area) 60.0 31.0 425 6 110, 000 95, 000 10. 0 43. 0 gg ggg gggg im ig 60 By comparison, beryllium copper alloy having the composition 0.65% Be, 2.70% Co, balance copper, 11i the form of 0.25 inch diameter rod material processed by solution annealing at 920 C., quenching and heat treat- A summary of the properties of a representative alloy ing at 480 C. for 3 hours and subsequently tested yat the of the present invention is presented in Table III wherein s211110 101111101010105 possessed 1611511@ '5119119118 0f 78,000

o D typical room temperature mechanical and physical propand 50,000 PS-1- a1 300 and 425 TSPVCUVSY The erties ofthe `alloy having the composition 1.5 Ti, 2.5% 11100111115 Otf 011151110113 O the bTflhum 0011961' 211101 ai l 0 e Sn, 0.5% Cr, balance Cu, are compared with those of 425 C W-S 14,000,000 PS1- 0011111211611 '0 111 V210@ Qf beryllium copper having the composition 0.4% Be, 2.6% 21,000,000 p.s.1. shown 1n the above table for the qua- Co, balance Cu. It will be apparent that the room tem- 70 ternary alloy of the present invention. At 425 C., the perature properties of the respective alloys are quite comproportional limit was only 18,000 p.s.1. for the beryllium- 'parable with respect to the materials (a) in solution aricopper alloy compared to the value of 32,000 p.s.i. listed iiealed condition, (b) in the solution annealed and heat above. Contrasted with the elongation and ductility treated condition and also (c) in the solution annealed, values for the new alloy listed in Table IV, the berylliumrzold Worked and heat treated condition. copper alloy specimens tested at the same temperatures were extremely brittle and the elongation and ductility values therefor were nil.

As previously indicated, silver may be additionally incorporated in the quaternary alloy in amounts up to about 1% without materially effecting the properties of the resulting all-oy. The properties obtained with 0.132 inch diameter wire treated as set forth below and made with alloys ofthe composition 1.5% Ti, 2.5% Sn, 0.6% Cr with amounts of silver ranging from 0.2 to 1%, the

balance being copper are summarized in Table V.

Table V Ulti- Yield Elong Elec. Permate strength (percond. cent, Treatment v tensile (0.1% cent (percent Ag strength offset. in2 .A.O.S.)

(psi.) p.s.i.) inches) 0. 2 S01. anu. at 875 C. 30 min.- 58,000 22,000

Aged at 450 C. for 2 hours 99, 500 Aged at 450 C. for 6 hours-- 95,000 Aged at 450 C. for 8 h0urs 93, 000 Aged at 450 C. for 14 hours. 88, 000 0. 5 Sol. aun. at 875 C. 30 min.- 5S, 000 Aged at 450 C. for 2 hours 85,000 Aged at 450 O. for 6 hours- 86, 000 Aged at 450 C. for 8 hours-- 87,000 Aged at 450 C. for 14 hours. 86,000 0.8 Sol. ann. at'. 875 C. 30 min" 57,000 Aged at 450 C. for 2 hours-- 100,000 Aged at 450 C. for 6 hours" 94, 000 Aged at 450 C. for 8 hours 92,000 Aged at 450 C. for 14 hours 88, 000 1.0 Sol. ann. at 875 C. 30 min-- 58, 000 Aged at 450 C. for 2 hours 08, 000 Aged at 450 C. for 6 hours.. 93,000 Aged at 450 C. for S hours 93,000 Aged at 450 C. for 14 hours. 87,000 62,000

Small amounts of phosphorus added to the alloy m-ade with initially oxygen-free copper depress the electrical conductivity appreoiably indicating that the phosphorus stays in alpha solid solution. From 0.02 to 0.05% phosphorus added to the alloy made with initially oxygen-free copper lowers the conductivity of the alloy containing 1.5% Ti, 2.5% Sn, 0.5% Cr, from 45 .to 35-37% I.A.C.S. but the strength ofthe :alloy is not affected to any appreciable extent.

The foregoing alloys were all made with initially oxygen-free copper. It was found that the tensile properties of the alloy made using tough pitch copper are generally about the same as those of the corresponding alloy made with initially oxygen-free copper provided that both alloys are processed in the same manner. The electrical conductivity is somewhat lower, however, as illustrated by the alloys containing 1.5% Ti, 2.5% Sn, 0.5% Cr. Comparison of the properties of the similarly processed alloys made with initially oxygen-free and tough pitch coppers showed a depression in electrical conductivity of from 45 to 37% I.A.C.S. attributable to the presence of OJZO in the tough pitch copper. Accordingly, the use of initially oxygen-free copper is generally necessary for obtaining electrical conductivities above 40% I.A.C.S.

While the present invention has been described herein in considerable detail with reference to speciic embodiments thereof, it is not desired to be limited thereby but it is intended to cover the invention broadly within the scope of the appended claims.

What is claimed is: Y

1. An age hardenable copper base alloy of at least copper content, said alloy consisting essentially of from 0.3 to 4% titanium, 0.5 to 5% tin and 0.05 to 2% chromium, the balance being substantially all copper with incidental impurities normally associated therewith.

2. An age hardenable copper base alloy of at least 90% copper content, said alloy consisting essentially of from l to 3% titanium, 2 to 4% tin and 0.2 to 0.8% chromium, the balance being copper with incidental impurities nor mally associated therewith.

3. An age hardenable copper base alloy of at least copper content, said alloy consisting essentially of from 1.3 to 1.7% titanium, 2.2 to 2.9% tin and 0.3 to 0.6% chromium, the balance being copper with incidental impurities normally associated therewith.

4. An age hardenable copper base alloy of at least 95% copper content, said alloy consisting essentially of from 1.3 to 1.7% titanium,V 2.2 to 2.9% tin and 0.3 to 0.6% chromium, the balance being initially oxygen-free copper, the titanium and tin being present in the alloy in the ratio of about 1:1.7 respectively.

5. An age hardenable copper base alloy of at least 90% copper content, said alloy consisting essentially of from 1 to 3% titanium, 2 to 4% tin, 0.2 to 0.8% chromium and an additional alloying element selected from the group consisting of silver and phosphorus in the amounts not eX- ceexling 1% and 0.05 respectively, the balance of the alloy being substantially all copper with incidental impurities normally associated therewith.

6. An age hardenable copper base alloy consisting essentially of from 1 to 3% titanium, 2 to 4% tin, 0.2 to 0.8% chromium and the balance substantially initially oxygen-free copper with impurities normally associated with such copper.

7. An age hardened alloy consisting essentially of from about 1.3 to 1.7% titanium, about 2.2to 2.9% tin, about 0.3 to 0.6% chromium, the balance being substantially all initially oxygen-free copper with impurities normally associated with such copper, said alloy being characterized by a combination of properties including a tensile strength of at least 90,000 p.s.i. and electrical conductivity of at least 40% I.A.C.S.

8. Copper-titanium-tin-chromium alloy made with initially oxygen-free copper, the content of titanium, tin and chromium of the quaternary alloy being about 1.5, 2.5 and 0.5% respectively, said alloy in the cold Worked and aged condition being characterized by a minimum tensile strength of 110,000 p.s.i. and electrical conductivity above 40% I.A.C.S.

References Cited in the le of this patent UNITED STATES PATENTS 2,059,557 Corson Nov. 3, 1936 2,189,198 Comstock Feb. 6, 1940 2,797,300 Hawthorne June 25, 1957 FOREIGN PATENTS 812,407 Great Britain Apr. 22, 1959 

1. AN AGE HARDENABLE COPPER BASE ALLOY OF AT LEAST 9/% C OPPER CONTENT, SAID ALLOY CONSISTING ESSENTIALLY OF FROM 0.3 TO 4% TITANIUM, 3.5 TO 5% TIN AND 0.05 TO 2% 